When a prior art dehumidifier operates, a blockage abnormality at the air outlet often occurs due to external environmental conditions or for the reason that the air deflectors cannot open normally. If the abnormality is not found out or not dealt with timely, as for a slight blockage abnormality at the air outlet of the dehumidifier, it will accelerate the aging rates of the compressor and the air outlet of the dehumidifier over the time, thereby reducing the service life of the dehumidifier; as for a severe blockage abnormality at the air outlet, it will directly threaten the operation of the dehumidifier, causing the dehumidifier to break down, decreasing the reliability of the dehumidifier, or even causing potential safety hazards of the dehumidifier. Therefore, how to avoid the product malfunction caused by the blockage at the air outlet of the dehumidifier has become a problem to be solved urgently.